1. Technical Field
This disclosure is related to image sensors and, in particular, to image sensors in which ghost images caused by reflection of infrared (IR) radiation are substantially reduced or eliminated.
2. Discussion of Related Art
Image sensors with both visible and near infrared (NIR) capability have been used in automotive sensors in such applications as driver assistance applications and safety applications, such as pedestrian, obstruction and sign detection, rear-view or back-up camera applications, etc. Such sensors can operate in a dual mode, which allows them to function both in daylight (in the visible light spectrum application) and night vision (in the IR application). This newly incorporated IR capability is made possible by the development and implementation of a number of process-level enhancements that expand the sensors' spectral light sensitivity to about 1050 nm, which is well into the NIR range of 750-1400 nm.
One drawback of this dual-mode capability is that the new sensitivity in the NIR range has resulted in IR ghost images being created. In certain situations, IR radiation can be reflected, such as, for example, by a redistribution layer (RDL) of the image sensor, and then detected by the image sensor. This introduces noise into the image sensor and, therefore, reduces the sensitivity of the image sensor.